I'm not real big on the 90's era fighting games that require a zillion buttons. At the same time, though, I didn't want to limit the game selection too much since I do play these titles once in a while. I settled on five buttons per joystick. Again, most games I like use one or two buttons with a few using more (like Defender and Stargate, for instance).

I'm jumping ahead a bit, but this shot helps understand the layout within this narrative.
(click to enlarge)

To increase the comfort level, though, I repeated the first two (most commonly used) of the five buttons on either side of the two lower sticks. This means that the left and right sticks have a full five buttons toward the inside of the control panel (right hand for the left stick, left hand for the right stick) but also have the first and second buttons (ctrl and alt in MAME) repeated on the opposite side of the stick. This means that if you opt to play most classic games on either of the lower sticks you can play comfortably left or right handed.

I've also come to discover that due to the fact player one has three first and second fire buttons scattered about, they can use whatever is most comfortable. It is sometimes more comfortable to use the fire button to the right of the lower stick or even the one all the way on the left side of the control panel in some games. This is also nice to vary your stance a bit if your hand or arm starts to cramp up or you are using the trackball or spinner instead of the stick.

In the center of the control panel I've placed the coin-up buttons as well as the player one and player two start buttons. This makes the center area something of the control region for the system especially when used with the shift functionality (discussed later in the software section).

As far as button layout and spacing, I spent quite a bit of time standing there and seeing where my palms and arms rested most comfortably without bumping the various controls. While the design might look a little crowded, it's actually quite ergonomic for me. There are gaps between the clusters where your palm can rest while using the various buttons. There is also space around the spinner for your hand to rest. The buttons are spread out next to the central player one stick in a kind of arc that makes reaching them fairly easy when pivoting on the palm of your left hand.

Prior to applying the formica, I drilled the holes for the buttons using a 1 1/8" spade bit. I basically eyeballed the hole placement, drilled the hole and dropped in a button as a placeholder. The player one stick in the center was fairly easy. I then moved to the lower left player one stick and worked out an arrangement. Because I wanted the right side player two stick to mirror the left stick (for visual symmetry), I had to devise a way to transfer the design.

I'm certain that this could have been approached more scientifically, but the method that popped into my head worked out rather nicely. Because the original control panel shape was established by using a half template flipped over (see Control Panel: Design), the joystick mounting plate cutouts and bolt holes were precise mirrors. I simply placed a sheet of paper over the left side joystick hole, pushed four bolts through the paper into their holes and cut holes in the paper where the button holes had just been drilled.

Here is a sheet of paper being used to template the existing holes relative to the mounting plate bolts.
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By flipping over this sheet of paper and aligning it with the bolt holes of the right side joystick I could precisely mark the mirrored button hole locations and be assured the symmetry was accurate. I repeated this process for all of the symmetrical sets.

This is the same sheet flipped and used on the right to mirror the button symmetry.
(click to enlarge)